This invention relates to a stator equipped with a planetary reduction gear device for transmitting reduced rotation of a starter motor to an output shaft, and more particularly to a shock absorbing device employed in this stator.
Japanese Patent Application Laid-open No. 11-117946 (1999) discloses a conventional shock absorbing device for a starter which includes a rotary disk engaging with an internal gear of a planetary reduction gear device and rotating when a predetermined torque is applied, a stationary disk brought into frictional engagement with this rotary disk, and a dish spring pressing the stationary disk toward the rotary disk. When an impact force acts between a pinion gear and a ring gear, an excessive torque is applied to the rotary disk via the internal gear. The rotary disk rotates in response to this excessive torque. The internal gear, engaging with the rotary disk, also rotates to absorb the transmitted shock.
However, according to the above-described conventional shock absorbing device for a starter, only one rotary disk and the stationary disk constitute the shock absorbing device. The torque transmittable through this shock absorbing device is small. For example, if this conventional shock absorbing device is incorporated into a starter employed for a diesel engine, the shock absorbing device will be subjected to a very high torque and the rotary disk will be forcibly rotated. Thus, due to undesirable rotation of the rotary disk, a torque actually transmittable through this shock absorbing device is small.